Kimberly
   Your use of the word "Sum" and the word "subtract" is confusing.  I
think you mean subtract.  If you were using a formula for that you would use
=D1-H3, not =SUM(D1-H3), although both give the same answer.
The following macro will do what I think you want.  This macro will operate
on the active sheet.  This macro loops through all the values in Column A
and searches for each of these values in Column E.  If the value is found,
the macro will place the value of the Column A item in Column I in the same
row as the column A item.  It will also subtract the value in Column H in
the row of the found value in Column E, from the value in Column D in the
row of the value in Column A.  This difference will be placed in the same
row as the Column A item.  That is a tongue twister!  Come back if you need
more.  Otto
Sub FindDups()
     Dim rColA As Range
     Dim rColE As Range
     Dim i As Range
     Dim FoundCell As Range
     Application.ScreenUpdating = False
     Set rColA = Range("A2", Range("A" & Rows.Count).End(xlUp))
     Set rColE = Range("E2", Range("E" & Rows.Count).End(xlUp))
     For Each i In rColA
           If Not rColE.Find(What:=i.Value, LookAt:=xlWhole) Is Nothing
Then
                 Set FoundCell = rColE.Find(What:=i.Value, LookAt:=xlWhole)
                 Cells(i.Row, 9).Value = i.Value
                 Cells(i.Row, 10).Value = i.Offset(, 3).Value -
FoundCell.Offset(, 3).Value
           End If
     Next i
     Application.ScreenUpdating = True
End Sub